Elaborating a bit more on what Connor said:
If you equalize too forcefuly, or too late, the sudden forceful increase of pressure can rapture your eardrum (but you would've probably notocied that).
What can also happen is, that instead of rapturing your eardrum a shockwave can also bounce off of it to the other side of your middle ear which is where the oval window located - it separates between your middle ear and your inner ear.
This shockwave can cause tinitus, and can also rapture the oval window, which if so happens/happened, you might need surgery, and might suffer partial/full hearing loss. Sounds like the case Connor mentioned above.
If the case is because of faulty equalization, it might be solved if you'll equalize more frequently (yes, even twice or thrice per meter), and less forcefully - no force is needed usually with frequent enough equalization. You can also try alternating between Frenzel and Valsalva, incase you feel one of them gives you more control on the force used. Maintaining a good body posture is also beneficial for easy equalization. If you dive with a hood, make sure it is flooded before you dive (making your outer ear full of water).
I suggest that in the next times you dive, you'll make sure which of the possibilities above might be causing that tinitus, if it's cold water, faulty equalization and such.
If it doesn't solve the problem, then I'de say you better get to an ENT or diving doctor ( not sure which is better for that

), and let him check that, you don't wanna risk permanent damage.
I think that if you're having bad sympthoms, you should not keep diving before them.
Good luck and keep us updated.
